Qualified Engineer Needed?

By | Blog, Scaffolding, Seismic Engineering | No Comments

Various standards and codes require that an engineer’s services are to be used for certain scaffold designs and installations.  Is that really necessary?  After all, thousands of scaffolds are constructed daily without any input from engineers.  Furthermore, do these engineers need to be qualified engineers or will any engineer be acceptable?  And even furthermore, aren’t scaffolds only to be designed by a qualified person.  And even more furthermore, doesn’t the U.S. federal Occupational Safety & Health Administration, OSHA, have one regulation that requires a “registered professional engineer” and other regulation that requires a “qualified engineer?”  Is there a difference?  Can you be a qualified engineer without being a professional engineer and can you be a professional engineer without being qualified?  The answer is yes, yes, yes and yes.

While OSHA requires that all scaffolds shall be designed by a qualified person, that is, an individual who has the ability to solve or resolve the issues at hand, certain scaffolds shall be designed by a registered professional engineer, while in other cases a “qualified engineer” is allowed.  That sounds confusing but it shouldn’t be.  To become a qualified registered professional engineer, an individual must meet the requirements set forth by the engineering profession.  First, an individual must hold a degree from a recognized accredited school—typically a college or university.  After successfully passing an 8-hour exam on the fundamentals of engineering, the candidate must then work under the supervision of a registered professional engineer for at least 4 years.  At that time, the candidate is allowed to take another 8-hour exam to verify that he/she is qualified to become a professional engineer.  The next step is for the professional engineer to apply for registration in the state or province in which he or she chooses to work.  Some states require additional examination before granting registration.  For example, California requires that the candidate pass an exam on seismic engineering.  Upon payment of a fee, in some states a substantial fee, the candidate is granted registration.  The registration is typically a 2-year registration; renewal in most states requires continuing education.  It is important to note that in addition to registration as a professional engineer, many states require a license to offer engineering services and of course a permit to conduct business in the state of registration.  Registration is indicated by the use of the initials P.E. in the U.S. and P.Eng. in Canada behind the engineer’s name.  Registration can be easily verified on state/provincial websites.

Registration as a “registered professional engineer” does not mean that you are qualified to design scaffolds.  Registered Professional Engineers must comply with the regulations of the state in which they are registered and also should comply with the ethics promulgated by the profession.  One of the tenets, and rules, is that engineers only practice within their field of expertise.  This means that not all registered professional engineers are qualified to design scaffolds.  Unfortunately, there are engineers who think they have the expertise but don’t.  Abuse of the title is often seen in the courtroom where supposed “experts” proclaim knowledge of scaffolding and regulations.  It appears the courts have allowed great latitude in the term “expert witness” to the consternation of qualified engineers. 

State and provincial boards monitor engineers’ activities and punish those who violate the rules.  The punishment ranges from letters of admonition to fines to license cancellation to imprisonment.  Interestingly, one can have a legitimate degree in a field of engineering but cannot offer engineering services without being a Professional Engineer.  In other words, unless you are registered, you cannot offer to provide engineering services.  Licensure is a serious controlled business.

Unfortunately, the term “engineer” had been diluted over time, to the frustration of the professional engineering community.  While railroad locomotive engineers are known to be a different type of engineer than discussed here, the term engineer is used in many other fields of endeavor, where it can create confusion.  While it is expected that professional engineers meet certain criteria regarding physics, material strength, structural analysis and other science fields, a “sales engineer” clearly is not a professional engineer.  Safety engineers do not meet the normal criteria for a professional engineer.  Custodial engineers and software engineers are other examples. 

What does a qualified engineer provide that a qualified person cannot is a legitimate question that deserves an objective answer. Qualified engineers can determine the strength of materials, components and structures to determine if a design is adequate for its intended purpose.  Engineers can evaluate existing situations for structural adequacy and compliance with applicable standards, regulations and industry practices.  In the case of scaffolding, the engineer must know the applicable regulations, the equipment being used in the design, and the impact the design will have on adjacent structures.  Depending on the scope of work, the engineer may also be required to understand other aspects of the project, including contracts and scheduling.

  A qualified registered professional engineer can provide the assurance that a scaffold is correctly designed, will provide the expected functionality and, most importantly, will not collapse!  A qualified registered professional engineer can analyze situations and offer creative economical solutions.  There is no doubt that many scaffolds can be designed by a qualified person, that is an individual with the knowledge and expertise to solve or resolve the issues at hand.  However, there are instances when the situation requires the special advanced education and expertise of a qualified professional engineer.  If you don’t know what those circumstances are, your qualified registered professional engineer should be able to tell you.

4 Tips for Safe Demolition

By | Blog, Demotion | No Comments

Are you aware of the regulations that govern demolition of buildings, bridges, and other structures? Did you know that regardless of the type of structure being demolished, the same set of OSHA standards apply?

Before you start tearing down that next structure, it’s important to have your safety protocol in place. You’ll want to be sure you comply with the appropriate OSHA standards, and that you’re taking the right steps to keep everyone in the area safe.

These four important measures will help get you on the right path to safe demolition. Read on to find out more.

The Basics of Demolition

1. Training Your Employees – Who is Responsible?

When it comes to demolition, it’s important to make sure that only experienced and properly trained employees perform this type of work. Contrary to industry belief, demolition is far from an unskilled task. Removing any structural member can destabilize the entire structure, and increase the chance of unplanned collapse. Only employees who have been trained thoroughly under the supervision of a competent person should ever be allowed to perform this type of work.

It is the employer’s responsibility to provide training for the specific work environments that will be encountered during the demolition process. OSHA clearly defines this duty in 1926.21(b)(2).

2. Provide Proper PPE – More Than the Simple Stuff

One would hope this would be obvious, but based on our anecdotal observations, one would be wrong! It is critical that all personnel not only have the correct equipment on hand, but they must be using it properly. This includes the basics – hardhats, safety vests, proper eyewear, hearing protection, gloves, steel-toed boots, etc.

Depending on the type of demolition, specialty project specific equipment may also be required. This could include fall protection, respirators, hazmat suits, and other items.

The Competent Person is responsible for making an assessment of the job site to determine what specific hazards may be encountered, and what equipment will be necessary.

3. Brace! Stabilize! Brace! Stabilize!

Question – would you remove the legs from a table while eating dinner from it, expecting it not to fall over (this is not a trick question)? Of course not! Similarly, would you think it is ok to remove structural supports from a bridge or building without first figuring out how to stabilize it? Let’s all pray the answer to that is “no” as well!

OSHA 1926.850(a) requires that prior to demolishing any structure, an engineering survey by a Competent Person must be performed. If the structure is complex, a Qualified Person (i.e. professional engineer) may be required to provide a sequenced demolition plan with engineered bracing and shoring layouts.

Demolition of large structures is tricky business. When in doubt, get an engineer involved.

4. Clean Up Properly

After demolition is complete, your work isn’t over. It’s also important to make sure the cleanup process is done safely.

Jagged concrete and exposed rebar are just two of many hazards encountered after the jackhammering has stopped. When possible, it is always recommended to utilize loaders and skid steers for debris removal. If hand removal is required, the competent person needs to be extremely vigilant to ensure employees handle the debris piles safely.

Final Thoughts

Thousands of demolition projects are completed safely every year. Following these tips (which are by no means exhaustive) along with the guidance provided in OSHA Subpart T will help ensure your next demolition project is done safely as well.

Need help with an upcoming demolition project?

Get in touch with our demolition engineers today and learn how we can help.

OSHA Update: Walking Working Surface Regulations

By | Blog, Facade Access, Fall Protection, OSHA Standards & Regulations | No Comments

Earlier this year, OSHA made headlines for the way it would revise the regulations regarding fall protection for general industry.

Did you know about the change?

As explained by the department itself, the modification accounts for modernization of technology along with updates to old regulations.

It’s important that building owners and managers understand the new developments. If you don’t, you could be facing fines from the government – or worse, accidents at your property with increased legal liability. 

There are several subtle changes in the regulations that have large implications.  Specifically, the changes in fall protection for facade access and building maintenance could potentially be costly for building owners.

Here’s what you need to know.

Standards for Window Washing & Exterior Maintenance

You’re probably aware of the complicated protocol that already exists around suspended scaffolding systems.

Now, a few new rules have been tossed into the mix for General Industry. OSHA has basically adopted various ANSI, ASME, and IWCA standards that were loosely followed in the past.  These are now law with clearly defined minimum requirements. 

The most important example is the minimum load any rope descent (i.e. boatswain or bosun’s chair) anchorage must now support. Prior to this update, a minimum of two to one safety factor was allowed (typically resulting in an anchor that could support around 1800 pounds). Now, ALL anchorages must be able to hold 5,000 pounds minimum.

Height standards are also changing for rope descent systems. No rope descent system can be anchored 300 feet above the base of a building barring some sort of extraordinary circumstance. Owners of buildings above this threshold will now have to accommodate the switch to powered platforms for window washing.

The ANSI/IWCA I-14 standard was widely considered the industry standard regarding anchorage testing and inspection. OSHA has now adopted the intent of this standard into the 1910.27 regulation. Building owners are now required to have their roof anchorages load tested upon installation, inspected annually, and load tested again every ten years.

The key takeaway from these changes is that OSHA is shifting much of the safety burden onto building owners and away from contractors.  Building owners are now REQUIRED to provide and have written certification that their anchorages meet the new standards.  Gone are the days where contractors could provide temporary anchorages to aid in window washing and exterior maintenance. 

Deadlines for Implementation

The new regulations for rope descent can be costly as mentioned, but OSHA is not allowing much time for building owners to get up to speed. There are no “grandfather” type exceptions in the regulation, just a set deadline of November 20, 2017 to comply.

What does it mean if your building is not ready by then?

To put it simply, you will not be allowed to legally wash your windows or undergo exterior maintenance work until it is. There are options such as boom lifts for lucky building owners that have properties accessible from the ground, but any type of rope descent access that requires overhead suspension is not allowed.

Penalties for Accidents

There are no new fines that have been introduced as part of this new OSHA regulation overhaul. Keep in mind though that OSHA already approximately doubled fines towards the end of 2015.   

Fines however, could be the least of one’s worries. As most building owners already know, potential legal damages in the event of a serious accident would far exceed any fines OSHA could levy. Throw a non-compliant building into the case, and the liability skyrockets. 

A Good Thing?

Those who will face the immediate brunt of these costs will certainly disagree that this is good change in the short run.  However, the new regulations have many benefits:

  1. Standardization of many loosely followed standards into one clear-cut law;
  2. Increased protection for workers. With permanent exterior maintenance systems now mandated, the potential for falls decreases;
  3. No more guessing – workers now know for certain whether the anchorages their lives depend on are safe for use;
  4. Long term savings in risk premiums as accidents are mitigated.

Regardless if this OSHA update benefits you or not, it is important that you understand it like the back of your hand.

Update Your Facade Access System Now

Dirty windows can make for cranky tenants. The sun’s harmful UV rays continuously pound building exteriors. If you are unable to wash windows or provide exterior maintenance against weathering, your building is in trouble.

The team at DH Glabe & Associates has the expertise to get your building compliant in the most cost-effective manner possible.

Feel free to reach out to someone on our team today to learn how we can help you.

FEA: The Next Best Stress Analysis

By | Blog, FEA, Finite Element Analysis | No Comments

The future of stress analysis has actually been around for over 60 years!

Finite Element Analysis (FEA), also known as Finite Element Method (FEM) is being used in the most modern applications, but the methodology has been effective for over half of a century.

What can it do for your company? Keep reading to get a brief overview.

What Is Finite Element Analysis (FEA)?

In a nutshell, the finite element analysis is a numerical method for solving problems in engineering and mathematical physics. It measures how a design will respond to weight, pressure and stress. Will it bend, break, or hold?

It’s best used when analyzing problems involving complicated geometry, loads, and material properties when analytical solutions can’t be obtained.

An analytical solution will do a stress analysis for trusses or beams, with mass concentrated on the center of gravity. Whereas FEA helps with more complex design geography.

It can help you understand:

  • The strength, heat transfer capability and fluid flow of complex objects
  • The performance and behavior of a complex design
  • The strengths and weaknesses of the design

The History of Finite Element Analysis

It can be traced as far back as A. Hrennikoff and R. Courant in the early 1940s, who used the methods of elasticity and structural analysis for aeronautical engineering.

Then in the late 50s and early 60s, China’s K. Feng used it for analysis of dam construction.

Today, the fundamentals are still one of the most reliable methods of stress analysis, trusted by people across the world.

According to Andres Gameros, “This analytical methodology has been used since the 1960s. In the years since its first use, Finite Element Analysis has grown and developed into a standard of design engineering worldwide.”

FEA has ushered in several commercial software packages which are used around the world, including Solidworks and LUSAS amongst many.

The Real World Uses for This Form of Stress Analysis

Today, this type of stress analysis is being used in:

  • Aircraft like the Boeing 787-9 Dreamliner
  • Complex bridge design
  • Some of the world’s biggest brands including General Motors (GM), Faraday Future, and Siemens
  • The oil industry
  • Aerospace engineering
  • High-end construction
  • Biomedical research and the textiles

As Autodesk’s Vikram Vedantham explained, “Structural FEA has the capability to influence engineering at multiple levels – from mainstream solutions that provide trends and insights to guide product development, to high-end solutions that aim to match real-world data.”

He added, “Picking features and capabilities is determined by the time of use, the persona involved, the level of depth, the geometry, the nature of the design, its use case and the size of the firm.”

So how does one pick a firm to take care of their FEA or any other type of stress analysis? Choose the firm with proven expertise, as well as a combined 5,500 projects, 32 years of combined experience and 54 combined professional licenses.

To learn more about how we can help you, please feel free to contact us.

Hanging Out

By | Blog, Resources, Scaffolding | No Comments

The suspension rope supporting a temporary platform is the single most important element of a suspended scaffold. You may not agree with this—too bad for you. What if the rope breaks? The platform can only go down and if you are at a considerable height, the result will be mostly unpleasant. Understanding this suggests that we should probably be sensitive to the condition of the rope to which we trust our lives.

What is a rope? A typical definition describes a rope as a cord that consists of twisted strands of material, such as hemp or wire. Of course, that begs the question of what cords and strands are. For that matter what is hemp? Can you smoke it? Perhaps not. How about this: a rope is a bunch of string or thread twisted together to make a bundle that can hold some weight. In the case of suspended scaffolds, the strings are normally wire although other materials such as hemp and polypropylene can be used, depending on the application.

Rope has been around just about forever. Evidence of rope’s use shows up in ancient Asia and Egypt. Wire ropes were invented about 1831 or so by Wilhelm Albert, a German involved with mining. He sought a solution to the very real problem of using chains where the failure of one link meant the failure of the whole chain. By twisting individual wires/strings into small bundles (strands) and then twisting the strands into a rope, (a big bundle), any defects are spread over more components, thus avoiding the problem of the weak link.

The industrial revolution encouraged rapid development of wire rope technology and the use of wire rope continued to increase. In 1841, John A. Roebling, designer and constructor of the Brooklyn Bridge, began manufacturing wire rope in America. Continued research and development discovered that more wires in the rope offered more flexibility and in 1884, researcher Tom Seale developed the parallel strand, where he used different diameter strands to make the rope. Figure 1 illustrates the Seale design.

While iron wire was initially used for metal ropes, steel wire began to be used in the late 1800’s. In fact, steel wire rope was first used in the construction of the Brooklyn Bridge in New York; the main ropes are still in use, demonstrating the durability and longevity of wire ropes. Over time, other wire rope designs have appeared, including the Filler strand, the Warrington strand and the Lang lay rope. Each design has its advantages and the job requirements will dictate the choice.

Wire rope is strong stuff, especially considering its relative light weight. Wire rope load capacity is governed by the rope material, configuration and diameter. While wire rope is available in an almost infinite number of diameters, normal diameters for suspended scaffolds are 5/16 or 3/8 inches. By its nature, rope can only handle tensile loads (you can’t push a rope!). However, the great advantage of a rope is that it can still handle the rated load whether the rope is 5 feet or 500 feet long. Within limits, that means the rope can hang down a 300-foot tall building and still support the same load as the rope will on a 50-foot tall building.

Adjustable suspended scaffolds typically use drum hoists or traction hoists. Drum hoists wind the wire rope on a drum or spool attached to the scaffold platform while a traction hoist passes the rope through the machine. Consequently, a drum hoist and rigging must support the weight of the wire rope while a traction hoist does not.
As with all materials, wire rope, while rather durable, can be damaged by improper handling and use and can also just wear out through continued use. Consequently, suspended scaffold erectors, and users, must be adequately trained in the potential hazards. For example, erectors must know how to handle the wire rope, including how to pay out the rope and how to wind it back up at the end of the job. The rope must be installed so the bottom end of the rope can hang free.

The attachment of the rope to its anchor is obviously critical to the strength of the suspension system. At a minimum, when loops in a rope are being made, a thimble and three fist grips (no u-bolts please) must be used, spaced at the manufacturer’s recommendations. The bolts must be tightened in compliance with the manufacturer’s recommendations; they must be re-tightened after the first loading of the suspension system, and then typically every day after that. The entire scaffold system including the suspension rope, must be inspected prior to each workshift. Properly trained suspended scaffold operators will know to inspect the suspension wire ropes every time the platform is raised or lowered to ensure that the rope is still in useable condition. It is rather undesirable to get the rope stuck in the traction hoist when 100 feet in the air. Even less desirable is having the suspension rope break when 100 feet in the air!

Suspended scaffolds get some impressive media coverage when failures occur since the incident leaves workers dangling high above the street below. Reporters nervously describe the precarious (and assume a dangerous) situation, leading the uninformed observer to believe that these devices are incredibly unsafe and a peril to the users. Since wire ropes on properly designed scaffolds can support six times the expected load, when the scaffold fails, it isn’t because the equipment is hazardous, but rather it is because somebody just plain screwed up. Don’t you be one of them!

5 Essential Facts About Facade Access Design

By | Blog, Facade Access, Fall Protection | No Comments

Facade design is an important aspect of any building project, but that doesn’t mean simply considering what the exterior of the finished building will look like.

Facade access design is an essential consideration. A good system will allow for maintenance to take place safely and at a reasonable cost. Maintenance operations can include setting up advertising, cleaning windows, fixing damage and more.

Here are five essential things you need to know about facade access design.

There are temporary solutions…

Temporary solutions for facade access include rope descent systems and hydraulic access platforms.

While these are relatively low-cost solutions, they have their drawbacks too. For example, a hydraulic lift will not reach the highest floors of a tall building, while rope descent work can take quite a long time.

… and permanent solutions

To secure a re-usable solution, a range of systems including monorail cradles or fixed davits might be favored depending on the jurisdiction (California, New York and other states have their own set of specific regulations).

Monorail cradles are useful on large flat or curved surfaces – they travel along a rail at the top of the building and can be lowered to the required level for access to the facade. They may not be appropriate to use for more ‘experimental’ facade designs.

For flat surfaces with less width, a fixed davit may be more cost-effective than a monorail cradle. Fixed davits are single arms which sit in one position and are used to raise and lower a maintenance platform.

Whichever of the two solutions you opt for, permanent or temporary, you will need to ensure that there is also a fall protection system to protect the people who are working on the facade.

Equipment needs to be inspected regularly

Just as facades need to be accessible, so does your facade access system so that it can be inspected and tested for safety at regular intervals.

OSHA 1910.66 states that all permanent equipment used to access a facade must be load tested when installed, and visually inspected every year. Additionally, OSHA 1910.27 states that each anchorages must be inspected annually and re-tested every 10 years.

Novel facade design calls for a novel approach

As modern architects create buildings with new and artistic facades, it’s important to think about how the facade will be accessible for maintenance purposes.

Sometimes, this will require an approach which is slightly different from the norm. This must be considered at an early stage of the project.

If the architect’s vision for facade design would result in a building which causes problems for facade access, there may have to be a compromise – or a novel approach.

It’s always good to get a second opinion

Our facade access design consultancy services allow building owners and architects to take advantage of our expert knowledge to create facade access designs that are safe and cost-effective.

We provide turnkey structural design and engineering solutions for new buildings, and can also help retrofit existing buildings to bring them up to code.  Contact Us today to find out how we can help with your façade access project.

I’m Digging Your Shoring Plan!

By | Blog, Resources, Shoring | No Comments

Due to the complexity and property line constraints of modern construction, earth shoring requires a solution that must conform to both engineering and safety guidelines during all stages of construction.

Here are the 5 key concepts to remember for an earth shoring design:

1. Applicable codes: The type of project will define the requirements for an engineered earth shoring plan. For instance, a design that allows for inches of deflection at a multi-story urban high-rise may not be compatible with AREMA requirements for railroad earth shoring. While a contractor may be able to get away with using a cantilevered design, a similar design that incorporates the locomotive surcharge loads into the analysis may fail simply by being out of tolerance for railroad deflection guidelines. In this case, the common solution is to add soil anchors to keep the design in compliance.

2. Material: This is typically a contractor preference. If a contractor has a substantial inventory of steel I-beams/H-piles and wood lagging, it is in the best interest of the client for the engineer to design the system accordingly. Piles may need to be spaced more tightly and the design may not be as efficient as sheet piles, but it does eliminate the need for the contractor to spend more money.

3. Sequencing: With most earth shoring designs, there is a sequence of installation that must be followed based on the applied loads that change with depth. For example, in a cofferdam design, if wale frames are required, the contractor may have to install the wale at a specified elevation prior to proceeding. This elevation may be above the final excavation depth, but the engineer should have determined that this is the maximum depth that the shoring can support in a cantilevered condition and/or without restraint at the base. This may be a result of deep excavations where the substrate alone at the base is not adequate to support the lateral load. Oftentimes, many scenarios must be analyzed to ensure that the members are not overloaded and the entire shoring design is code-compliant at any given stage.

4. Embedment Depth: As a general guideline, the minimum embedment depth of a pile must be 75% of the retained height to ensure adequate development and base restraint.

5. Workers at the Top of the Excavation:  While the designer may account for the surcharge loads at the top of the excavation, it is also important to consider the impact of workers. If a guardrail is required based on project conditions, then it must be OSHA compliant and any loads/connections required shall be accounted for in the design of the pile. Common practice is to weld a guardrail post at the top of the pile, but this must be checked not only for load application, but also for maximum spacing.

Engineered shoring plans are critical components of construction plans, and a well-thought out design will save the contractor both time and money. As the saying goes,”Think before you dig!”

5 Impressive Things Built (or Fixed) Using Cofferdams

By | Blog, Cofferdams, Shoring | No Comments

Everyone knows about dams. But have you heard about a cofferdam?

Cofferdams have been around for a long time. People have used these when excavating very large plots of land or building foundations of water-based structures such as bridges or piers. The cofferdam keeps water from flowing into these sites, ensuring a dry foundation.

The cofferdam has been used to build and fix some impressive things. Check out the five most inspiring objects constructed by using these fascinating dams.

5 Impressive Things Built (or Fixed) Using Cofferdams

Cofferdams have helped civilizations divert water, gain new territory, build dry structures safely, and even recover history. They can be as simple as a pile of sandbags set up to use as a barrier during wartime or complex as a double sheet piling used in modern-day bridge construction.

While today the cofferdam is particularly useful for earth shoring engineering projects, it continues to be used in the engineering world as a helpful tool in water diversion projects.

1. Battleship U.S.S. North Carolina

Because ships are a water-borne craft, their preservation often depends upon a dry work environment. When it comes to this battleship located in Wilmington, North Carolina, the use of a cofferdam will integrate a memorial walkway for visitors and water-free access to the battleship for preservation and repair work.

The project, nearly six months away from completion, is unique because it won’t rely on the cofferdam for underwater construction. This battleship will be open to visitors and kept looking sharp above water.

While this battleship will cost a hefty $8 million, it will, in fact, be a permanent installment. This is another great aspect of the cofferdam: it can be both temporary or fixed. The permanent cofferdam enables future maintenance and repair work on structures like the U.S.S. North Carolina.

2. The Hoover Dam

It may seem counterintuitive to say that dams are made by using dams. But with this impressive dam that’s become an icon of the American road map, cofferdams were a huge part of the construction.

The Hoover Dam construction was an architectural and engineering feat in Nevada in 1933. Before the dams were installed, workers removed 250,000 cubic yards of silt from the river in order to ensure a solid starting foundation.

Two cofferdams were required to make sure the construction was dry and water-free. Both were made from earth and rockfill, and relied on an additional rock barrier to prevent any additional water seepage. While some people were worried that the spring Nevada floods may damage all of this foundation pre-work, the damming worked and construction went along as planned.

3. Ancient Roman Bridges

When we said that the cofferdam has been around for a really long time, we meant it. For thousands of years, civilizations have found the cofferdam useful, and you see this in many of the bridges of Ancient Rome.

Early populations relied on more basic forms of the cofferdam in order to control waters for drinking supply, irrigation, and land control. Often this entailed the diversion of a river. Legend has it that King Cyrus of Persia used the cofferdam in order to divert the Euphrates River in his pursuit of the city of Babylon. This meant that an entirely new empire was established based off of the use of this dam alone!

Similarly, the Romans made use of this handy type of damming when bridging the Danube River. Trajan’s Bridge, built as a result of cofferdam wood pilings, enabled the Romans to travel to contemporary Romania. This bridge totaled nearly 4500 feet in length.

4. The Tapan Zee Bridge, New York City

The Tapan Zee provides a great example of how cofferdams still help with important construction feats today. This incredible bridge spanning the Hudson River cost nearly $4 billion to construct. Its completion would not have been possible without the use of the cofferdam.

A complex software was used to design the steel dams, 90 feet by 45 feet, used in construction. The software also took soil type into consideration. Because the Hudson contains a lot of river silt and soft deposits, the Tapan Zee dams had to be backfilled in order to create a solid base for the bridge piers.

5. The La Belle ship

The La Belle shipwreck has long been an icon of the Texas coast, and the cofferdam made sure that La Belle remained a fixture of seventeenth-century history.

In 1687, this ship crashed along the shoreline as a result of poor weather and difficult seas. Manned by a New World explorer, this ship was the last of four ships sent to explore the unknown coasts. When La Belle crashed and sank, it became sealed in mud for over three hundred years.

In 1995, an archeological team discovered the site of La Belle’s sinking. Such a recovery requires a lot of complicated engineering. The Texas Historical Commission constructed a cofferdam system around the sunken ship. This elaborate system cost over $2 million.

The mission was successful, and in 1997 the full extent of the treasure was known. Hundreds of incredibly preserved artifacts and much of the ship’s original structure were recovered. If it weren’t for the cofferdam, we would never know this history.

Cofferdams of the Future

There’s no doubt about it: the cofferdam is versatile, useful, and amazing. It has enabled people to bring history back to the surface, cross rivers, and construct impressive architecture. The cofferdam will continue to be an essential part of contemporary engineering projects.

At DH Glabe & Associates, cofferdams are our bread and butter when it comes to earth shoring engineering. To date, we’ve completed over five thousand company projects in thirty-two years, relying on the expertise of over fifty professional licenses. We assist with both civil and commercial projects using a variety of technology, including H-piles, mechanically stabilized earth walls, sheet piles, geofabric, and secant pile walls.

Earth shoring is not all we do. No matter the size or type of your engineering project, at DH Glabe & Associates we pledge to be with you every step of the way. Contact any of our construction engineering experts today to learn about what we can do turn your project into a reality this year.

What You Need to Know: Earthquake Resistant Buildings

By | Blog, Seismic Engineering | No Comments

Earthquake resistant buildings save lives. They limit property damage and comply with the latest seismic building codes.

If you do business in high earthquake hazard areas, here’s what you need to know about seismic building codes.

1. Seismic Building Codes are Getting Tougher

In 2015, Los Angeles overhauled their seismic regulations. 15,000 buildings needed retrofitting to better withstand the effects of earthquakes.

For decades, safety advocates worked to pass ordinances strengthening two types of structures. First were the brittle concrete buildings on L.A.’s major boulevards. Second, the boxy wood-frame apartment buildings built on top of carports. Over 65 people died when these types of buildings collapsed during earthquakes in 1971 and 1994.

2. Designing Earthquake Resistant Buildings is a Regional Endeavor

Building codes are based on the base shear formula. This formula measures how much earthquake-generated shear force will try to push the house off the foundation base. The simple formula multiplies the expected ground acceleration by the building’s weight.

But there’s no set amount for anticipated ground acceleration. For example, Los Angeles anticipates a different base shear than the California Building Code does.  The International Existing Code’s ground acceleration is different still. Keeping this in mind, it’s always best to use a base shear that’s tailored to your geographic region.

3. It’s Not Just the Building, It’s The Ground Underneath

Earthquake resistant buildings are great. But let’s say a building’s foundation sits on soft soil. Despite the advanced engineering techniques used, it could still collapse in an earthquake.

But, if the soil beneath a structure is solid, engineers can improve how the entire building foundation system responds to seismic activity.

One example is base isolation. In this method, a building is floated above the foundation on bearings, springs or padded cylinders. A solid lead core is used for vertical strength with rubber and steel bands for horizontal flexibility. This allows the foundation to move without moving the structure above.

4. Seismic Engineering has a Bright Future

All around the world are examples of newer structures withstanding earthquakes. One example is the Transamerica Pyramid in San Francisco.

During the Loma Prieta quake, the building shook for more than a minute and the top floor swayed a foot side to side. A deep concrete and steel foundation and a buttressed exterior allowed the building to escape structural damage.

Sensor readings were taken from the building’s frame and processed by the U.S. Geological Survey. The results showed the building could withstand an even larger seismic event.

The future of seismic engineering doesn’t just look forward. Retrofitting older buildings is as important as new construction. One bright spot is engineers are effectively and economically adding base-isolation systems to existing structures.

After the 1989 Loma Prieta quake, engineers retrofitted the city halls of San Francisco, Oakland, and Los Angeles. These earthquake-resistant structures will be tested. When and how remains to be seen.

The Final Analysis

More jurisdictions are mandating seismic building code compliance. That’s where DHG comes in. Our experience with earthquake resistant design ensures your clients’ buildings will comply with the latest codes.

To see our seismic engineering services up close, contact us for a consultation.

Stresses of Thermal Loads

By | Blog, Resources, Uncategorized | No Comments

A thermal load is defined as the temperature that causes the effect on buildings and structures, such as outdoor air temperature, solar radiation, underground temperature, indoor air temperature and the heat source equipment inside the building.

ASCE 7-15 section 2.3.5 and 2.4.4 specifically mention thermal and other self-straining loads are to be considered, where applicable. For many cases, thermal movements cannot be restrained and instead designs need to allow for the structure/equipment to move thermally otherwise stresses in either the restraints or in the structure/equipment may cause catastrophic failures.

Different materials have different expansion rates. Structures or items with different types of materials connected by fasteners or adhesives can warp and break at extreme temperatures. For example, PE pipe will expand/contract around ten times more than steel pipe.

Historically, thermal stresses have caused failures in railroad tracks, roads and building facades and even electronic devices. Understanding these effects, and how to minimize them, reduces the risk of damage or failure at extreme temperatures and prevents having to perform costly repairs.

For example, a 200 ft long PE pipe can change in length by 1/8 of an inch per degree (F) of temperature change. If this movement is restrained, stresses in the pipe and the restraints will be generated. Depending on the strength of the restraint and the buckling strength of the pipe, the restraint could fracture or the pipe could buckle. Buckling pipes can injure anyone working next to the pipe and could also cause leaking of the pipe. Damage and injury could also occur when a restraint breaks.

Even sidewalks are not immune from thermal stresses. Recently a large section of 4’ wide sidewalk was installed about a block long. Thermal expansion joints were not provided at adequate spacing. During a hot summer day, a loud explosion was heard throughout the neighborhood. The sidewalk had buckled and one of the sections of sidewalk had shattered. The concrete was left uneven and damaged requiring removal and repair of the damaged area of the sidewalk. Additional thermal expansion joints were provided to hopefully prevent future problems.